In semiconductor fabrication, in material removal processes such as chemical mechanical polishing (CMP), etching, or etchback, the stopping point is conventionally controlled by employing etch stops or by setting particular removal times. However, such methods do not guarantee homogenous and controlled material removal. Often if the removal rate or removal homogeneity is not sufficiently precise, the currently processed wafer is misprocessed and corrective action is performed only for subsequent wafers. This may lead to substantial losses.
A need therefore exists for methodology enabling in-situ removal rate definition and removal homogeneity-over-radius definition as well as in-situ corrective action.